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Rancid odor in final product, but raw ingredients still smell fine
Hello,
I am formulating a face moisturizer (see formula below) for my small business. Currently undergoing stability testing, and it has been 1 month since making the product. Everything is good so far, except the odor. The final product has gone from a faint peppery scent (from the black seed oil) to a rancid odor. Most raw ingredients used, particularly the oils and butter, were new when making the product.
I’ve been trying to figure out what has caused the rancidity. I checked the raw ingredients, and they have not gone rancid and still smell as they did when I first opened them. The pH of the final product still remains the same between 4.5 and 5.0. Any ideas of what could be causing the odor? Is there anything I need to add or change in my formula to avoid the rancid odor?
Heated Water Phase:
Water q.s. 100%
Sodium phytate 0.2%
Propanediol 4%
Glycerin 4%
Sepimax zen 0.3%
Heated Oil Phase:
Olivem 1000 2.5%
Glyceryl stearate 1%
Cetyl alcohol 1.3%
Refined shea butter 2%
Isoamyl laurate 2%
Pomegranate sterols 1%
Cool Down Phase:
Allantoin 0.3%
Dimethicone 1%
Black seed oil 1.5%
Irish moss extract 0.2%
Sodium benzoate 0.35%
Lotioncrafter PE 9010 1%
Mixed tocopherols T50 0.1%
Lactic acid (pH adjuster)
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22 Replies
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Forgot to mention that sodium phytate, sepimax zen, and allantoin are the only older ingredients that I have because it takes me so long to go through them. Could the sodium phytate be the issue here? Maybe it has lost its chelating properties? I’m not really sure if that would cause a rancid odor though, and the color/appearance of the final product has not been affected.
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Check for micro contamination. Even if clean, your product is very poorly preserved.
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After reading the discussions around here, I was under the impression that a good preservation system includes PE 9010 (bactericide) + sodium benzoate (fungicide) + chelator + glycol/diols + pH 4.8.
Should I add caprylyl glycol? I thought propanediol and glycerin would fall into that category of glycol/diol preservative boosters.
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Sorry! My error - was distracted with “Lotioncraft” and missed the PE. That should be a good system.
Still - have you checked for micro contamination? That is a reasonable source of rancid odor.
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Hi,
Micro-contamination is 100% possible, but I suspect the oils, in this order:
1. Black seed oil: VERY prone to oxidation due to its high content of unsaturated fatty acids and volatile compounds; even the refined version can oxidize rapidly if not protected enough;
2. Shea butter: even the refined version can contain oxidized lipids, depending on processing/storage/handling;
3. Pomegranate sterols: if they contain residual unsaponifiables or are not fully deodorized, they could contribute to off-odors.
Ideally, you would perform some knockout experiments to find out the “culprit”.
If you don’t have time to do the said knockout experiments and want to keep the black seed oil, I would start by using a higher % of antioxidants (as obviously 0.1% is not working): either 0.15% tocopherols (0.05% in the oil phase, and 0.1% in the cool-down), or 0.05% tocopherols+ 0.05% rosemary extract+ 0.05% ascorbyl palmitate. Of course you could go higher/lower with the second suggestion, but you have no way to know, other than experimenting.
Different antioxidants work through different mechanisms, and combining them can lead to a synergistic effect (the overall antioxidant capacity is greater than the sum of individual antioxidants).
Also you said you are performing stability tests: it’s curious to me that the rancid smell did not come up after you exposed your emulsion to repeated cycles of high and low temperature, and it developed after one month.
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This reply was modified 2 weeks, 4 days ago by Aniela.
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Agreed. As you used the term ‘rancid’, a term that in cosmetics typically gets applied to oils…. this makes sense. Most people starting out buy just hideous grade oils. Once an oil is deemed unusable by the industry due to degradation….it is NOT thrown away…but sold to the repackers. Many of my peeps have told me that they receive rancid oils from the repackers….the day it arrives.
If you are not using something like ICSC out of Denmark…then your lipids will always be ‘suspect’ unless you are testing them.
As with any cosmetic….. do a ‘knock-out’ test. Make a small batch …. each time removing one of the listed ingredients….and bingo…. pretty soon you will know what is causing it. 😉 If not one of the lipids…. then keep working through the list…with the most plausible candidates first.
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Next thing I would knock out….would be the ….’rich in Sulfur’ Irish moss. 🤣
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This reply was modified 2 weeks, 4 days ago by Graillotion.
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This reply was modified 2 weeks, 4 days ago by
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Wow, I did not know that about repackers. That’s interesting, and also unfair. I’m always careful with where I get my ingredients from, but I guess that still won’t matter especially with oils.
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Thank you so much, your response is very helpful.
Yes, I did not notice any odor after freeze-thaw cycles. The rancid odor is apparent after 1 month in 45C and also after 1 month of the product being opened daily at room temp to mimic regular use.
You bring up very good points, and I will do some knock-out experiments. This is my first time working with oils like this; I typically only use esters like squalane, jojoba, or C12-15 alkyl benzoate.
You also mention that I could increase the tocopherols by adding 0.05% with the oil, and 0.10% in the cool-down phase. Is there a difference between doing it this way versus adding all 0.15% in the cool-down phase? I will consider adding ROE and ascorbyl palmitate; that seems like it would be a good idea.
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Think of this like a “conflict situation”: the sterols and the oils in the cool-down phase are the damsels in distress, and the tocopherols are the knights in shiny armor. The first knight (in the oil phase) will let himself be killed or badly hurt to protect the damsel (sterols in your case) and the second knight (in the cool-down phase) will fight to keep the other damsels (oxidation prone ingredients) safe and sound.
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I wanted to chip in on @Aniela‘s nice metaphor with a funny comment, but I woke up with zero creativity today 😅. I’d first start with including both Dimethicone and Black Seed Oil to the oil phase and removing (or bringing up to 0.01%) your Irish Moss Extract. It’s best to have all the oily-heat resistant-ingredients in the oil phase since oils within micelles oxidize less that free oils. Now, it matters which type of mixer you’re using: a high shear homogenizer works best to create more homogeneous emulsions, while low shear would probably leave part of your oils as free oils in your system (and more prone to oxidation). Now, I like the knight metaphor, only Tocopherols are more like Lord Farquaad (cheap reference to my favorite Shrek movie), while something like Tinogard TL is kinda Christian Bale in The Dark Knight (sorry no sorry Ben Affleck). I believe nature was a bit lazy when synthesizing Tocopherols and didn’t want to handle some nice amines and a couple of more cyclization reactions…but she (yes, she) made Henry Cavil and Amy Adams, so it’s fine.
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😃 Thank you for chipping in. Nice touch for 8am- I suppose you had your coffee already.
I love Shrek, so I’ll stick to his story:
Tinogard, it’s like Princess Fiona for some of us- as hard to find/get as she is. Maybe easier for @simplepimple , I don’t know.
Now, adding the Black Seed Oil to the oil phase would be like handing Fiona to Lord Farquaad. The oxidative stability of this oil is VERY low, so it has to go in the cool down phase. But I do agree that adding it at claim levels, as you suggested with the moss extract, could remove the issue.
Not finished yet😇
Would you mind to help me on a different topic, please? (sorry @simplepimple )
Someone is coming from the US, and I want to take advantage and order acetyl zyngerone, n-acetyl glucosamine, and hexylresorcinol, but these will be exposed (during transport to the US destination) to a temp of 50-55C for about 24 hours(they checked with the company). Would these ingredients be rendered unusable? Thank you.
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I’m loving all the metaphors and humor here. Thanks for all the help!
@Aniela I don’t mind at all. I learn more from all the questions and discussions here!
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Those ingredients have more chances to resist if they are in solid/powder form, in a tightly sealed package (inert gas should be a lot to ask, but at least some vacuum would be nice) and not exposed to direct sunlight 🤓
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Thank you. No such thing: they will be in a ordinary cardboard box, in a truck.
PS - You’ll see I’ve just asked in a separate post-I thought you took it like a silly question so you won’t answer. Sorry, I know, overthinking doesn’t help…
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I mean the individual packages will be sealed, but only like any other powder ingredient, nothing special like vacuum. Also there will be no sunlight, only sun-heat😁
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For a separate product that I had been testing, I formulated a face oil consisting of 15% black seed oil, 0.1% tocopherols, and q.s. squalane. After two months at 45C, the strong scent of the black seed oil dissipated, but was not rancid. Would you recommend adding ROE along with the tocopherols for the face oil? Or is the tocopherols on its own enough in this case?
And jumping back to the original problem of this post with the moisturizer, can black seed oil be ruled out from being the issue since it seems to have done just fine in the face oil, leaving shea butter and pomegranate sterols as the culprits?
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This reply was modified 2 weeks, 4 days ago by
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Hi! No worries….and I think you’ve got a nice answer on that other post 🤓. For what you described, there shouldn’t be any issue.
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Thank you. For everything: I’m “swimming” through the emulsifiers (Q&A in the forum) and I’m grateful for your answers. Some additional questions will definitely come up after my “swimming” lesson😇
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This reply was modified 1 week ago by Aniela.
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This reply was modified 1 week ago by
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I have to add that isoamyl laurate over 1% will develop also an unpleseant smell. I think you have pooor antioxidant sistem there ( add rosmaryn antioxidant , Phenethyl Alcohol, Caprylyl Glycol) if you want to go green and BHT if you don’t. Also there are better chelating agents and more potent. try to mix black seed oil with tocopherol ( beforre adding in the emultion)
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Oh, I did not know that isoamyl laurate can have a smell at higher percentages. I will keep that in mind as I do some knock-out tests. I will also add ROE for a better antioxidant system.
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Tocopherol is a weak antioxidant. Use BHT and increase the concentration of chelators.
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